1. Field of the Invention
This invention relates to an electrostatic reproducing apparatus for electrostatically reproducing an image of an original by solid-state scanning using a charged particle modulating electrode (including an ion modulating electrode) unit, and an electrostatic reproducing apparatus having a solid state scanning system of wiring formed on a substrate for a charged particle modulating electrode unit.
2. Description of the Prior Art
An electrostatic reproducing apparatus is one of several apparatuses for reproducing on recording paper an image signal of information supplied from a computer, information transmitted through a communication line, or information obtained by converting an image of an original into an electric signal by a solid state image sensor, such as a CCD (charged coupled device image sensor). Various types of electrostatic reproducing apparatuses have been proposed. In an electrostatic reproducing apparatus an image signal is formed on a charge receptor, such as a photosensitive material, or a dielectric or an electrostatic recording paper. There is an electrostatic reproducing apparatus of such type that an electrostatic latent image is formed on a dielectric by using an ion modulating electrode unit, a kind of electrostatic latent image-forming means, which is adapted to modulate in accordance with image signals the corona ions generated by a corona wire. FIG. 1 is a schematic diagram illustrating the construction of an example of the above-mentioned type of electrostatic reproducing apparatus. In this apparatus, an image signal obtained by subjecting an image of an original to photoelectric conversion by a solid state image sensor, such as a CCD, or a signal representative of electric information from a computer or a communication line, is supplied to a signal processing circuit 1, and the resulting signal is then sent to an ion modulating electrode unit actuating or drive circuit 2. Reference numeral 3 denotes a control circuit including a clock generator for making the extraction timing of signals from the signal processing circuit 1 and actuating circuit 2. An ion modulating electrode unit 4 consists of a common electrode 4a which is a continuous layer of a conductive material and a control electrode 4b which is a segmented layer of a conductive material, which are formed on the opposite surfaces of an insulating layer, and has a single row of, or a plurality of rows of ion passing apertures 4c, through which control electrode 4b is adapted to receive an image signal from the actuating circuit 2. A corona ion generator 5 containing a corona wire 5a therein is disposed above the ion modulating electrode unit 4, and a rotary drum 6 consisting of a dielectric thereunder. A developing unit 7, a transfer electrode 8, a separating pawl 9, a charge eliminating electrode 10 and a developer cleaning blade 11, which are necessary for carrying out a conventional electrophotographic process, are disposed around the rotary dielectric drum 6, and a fixing unit 12 is disposed on the downstream side of the rotary drum 6. The rate of passage of ions, which are generated by the corona ion generator 5, through the ion passing apertures 4c is modulated with a control signal applied to the control electrode 4b of the ion modulating electrode unit 4. Thus, an electrostatic latent image corresponding to the image information to be reproduced is formed on the dielectric constituting the rotary drum 6. The electrostatic latent image thus formed is developed with a developer in the developing unit 7 to be then transferred by the transfer electrode 8 to recording paper P. The recording paper P is then separated from the rotary dielectric drum 6 with a separating pawl 9 to be fixed by the fixing unit 12 and ejected outside of the apparatus.
The ion modulating electrode unit used in the above electrostatic reproducing apparatus is provided with a single row of, or a plurality of rows of, ion passing apertures 4c, and a rate of passage of ions through the apertures 4c is modulated with voltages applied to the common electrode 4a and control electrode 4b. Accordingly, the control electrode 4b consists of segmented electrode members which are independent of each other, each of the independent electrode members having one of the ion passing apertures 4c, each of the independent electrode members being adapted to receive an image signal from the actuating circuit 2. The number of the ion passing apertures 4c is, for example, as large as 5-15/mm, so that the number of electric lead lines extended to the control electrode members corresponding to the ion passing apertures 4c becomes enormously large. In order to increase the resolution of the reproducing apparatus, it is necessary that the number of the ion passing apertures 4c be increased. Consequently, the number of the electric lead lines extended to the control electrode members becomes increasingly large. Then, as shown in FIG. 2, all ion passing apertures and all corresponding control electrode members are divided into a plurality (for example 15-16) of groups G1-Gn, and the same image signal is applied simultaneously to the control electrode members as common wire in the corresponding positions in each of the groups G1-Gn (for example, a control electrode member Ce1 in a minor electrode unit 4b1 in the group G1, a control electrode member Ce2 in a minor electrode unit 4b2 in the group G2, . . . a control electrode member Cen in a minor electrode unit 4bn in the group Gn), the group being modulated with a voltage applied to minor common electrode units 4a1, 4a2 . . . 4an. This allows the number of electric lead lines extended to the control electrode members to be reduced. (In this structure, the common electrode 4a is disposed facing to the corona ion generator 5 as shown in FIG. 1). This control system is known as a group control system or a solid state scanning system. The group control system, which consists of a switching circuit constituting a drive circuit for supplying an image signal to the control electrode, a hold circuit, and a shift register, is advantageous in that it has small dimensions and capacity.
However, in an electrostatic reproducing apparatus employing the above-described group control system, the dividing positions of minor common electrode units 4a1, 4a2 . . . 4an in the groups G1, G2 . . . Gn and those of the minor control electrode units 4b1, 4b2 . . . 4bn in the same groups are in agreement with one another, so that the density of an image becomes uneven in the boundary portions of these minor electrode units. This problem will be described with reference to FIG. 3. FIG. 3 is a schematic representation of that portion of a divided ion modulating electrode unit which is in the vicinity of a boundary between two groups G1, G2. In this example, the passage of ion flow (positive ions) is blocked in the group G1, and passed in the group G2, by voltages applied to the minor common electrode units 4a1, 4a2. In a group control system using such positive ions, an electric potential of the minor common electrode unit 4a2 which passes the passage of an ion flow is higher than that of the minor common electrode unit 4a1 which blocks the passage of an ion flow. Accordingly, a part of the positive ions generated by a corona wire 5a in a region of the group G2 tends to advance as shown in broken line toward the minor common electrode unit 4a1 having a lower electric potential. The same phenomenon occurs in some cases in boundary portions (not shown) of groups G2, G3. Therefore, the ion flow passing through the ion passing apertures 4c in the boundary portion of each group is decreased to cause the amount of charge held on a charge receptor to be decreased. As a result, the density of those portions of a reproduced image which correspond to the boundary portions of the groups is decreased. This would cause the density of a reproduced image as a whole to become uneven.
In a conventional electrostatic reproducing apparatus, in which the electrostatic reproduction of an image of an original is carried out by using an ion modulating electrode unit and on the basis of the above-mentioned group control system, a group control system of wiring is provided separately from the ion modulating electrode unit and connected thereto with electric wires and connectors. Accordingly, such an electrostatic reproducing apparatus requires very complicated assembling and wiring operations. This causes the efficiency of manufacturing the apparatus to be decreased. In such an electrostatic reproducing apparatus, the resolution thereof cannot be improved to a great extent due to the complicated construction thereof. In another type of electrostatic reproducing apparatus using a multi-stylus electrode, the above-mentioned problem has been solved by combining the multi-stylus electrode and a group control system of wiring together on a single substrate by using through-hole wiring. However, in the ion modulating electrode unit, which consists of, as mentioned above, electrodes of a conductive material and an insulating layer sandwiched between the electrodes, it is difficult as in the multi-stylus electrode to combine the group control system of wiring and the ion modulating electrode members together due to the problems of electrode material and chemical etching technique.